Spinach is one of the healthiest and tastiest vegetables ever, and growing spinach in containers is easy, you can even grow it indoors on a windowsill. Sow seeds 1/2 inches deep directly in containers or in a seed tray. Seedlings will germinate in 5-14 days depending on the variety and growing conditions. If you have sown seeds in a seed tray wait until 2-3 true leaves appear in each plant and then transplant them into the original pots carefully. For growing spinach in pots, choose a pot that is least 6-8 inches deep. Provide each spinach plant a space of 3 inches, if you want to pick large leaves give more space to each plant, 5 inches. Continue reading the tutorial in the source.
SOURCE:http://www.gardenoholic.com/how-to-grow-spinach-in-pots-and-containers/